Disc brake having at least two friction rings

ABSTRACT

A disc brake for a motor vehicle having at least two axially stationary friction rings being connected to a rotatable hub. The disc brake comprises several brake pads cooperating with the associated friction rings during a braking operation. A favorable structural overall design of the disc brake is achieved by a brake caliper straddling all friction rings and the associated brake pads and including a first actuating device in a brake caliper portion that extends axially beside the friction rings, and a second actuating device that is arranged between two friction rings and acting axially on both sides. Said actuating device acts on the brake pads arranged between two friction rings and is arranged so as to be displaceable relative to the brake caliper.

TECHNICAL FIELD

The present invention relates to a disc brake having at least twofriction rings connected to a rotatable hub. In this arrangement, thedisc brake comprises a plurality of brake pads interacting with theassociated friction rings during a braking operation.

BACKGROUND OF THE INVENTION

Thus, WO 98/25804 A1 discloses a design of a disc brake with two brakediscs for a motor vehicle being integrated into a wheel suspension. Inthis arrangement, especially an actuating device of the disc brake isarranged in a steering knuckle pertaining to the wheel suspension. Thetwo brake discs are connected to a rotatable wheel hub in ananti-torsion and axially displaceable manner. Brake pads cooperatingwith the brake discs are displaceably guided on a brake housing, withsaid brake housing being mounted on the vehicle. For applying a discbrake of this type, the actuating device is used to apply the brakediscs and the brake pads against each other by way of axialdisplacement. As this occurs, corrosion impairs the ease of displacementof both the brake discs and the brake pads that is important for thebraking function.

Further, international patent application WO 98/41778 A1 describes amotor vehicle disc brake with two brake discs, which, at an axialdistance, are stationarily arranged on a wheel hub. Associated brakepads are displaceably arranged within a combined disc brake device.During a braking operation, the brake pads can hence be urged by way ofaxial displacement against the respectively associated brake disc. Tothis end, the disc brake device comprises a first fixed-caliper-typecomponent, which is mounted on the vehicle and interacts with a firstbrake disc by way of brake pads. In order to urge the brake pads againstthe associated first brake disc during braking operation, thefixed-caliper-type component has a hydraulic actuating device on bothsides of the first brake disc. The fixed-caliper-type component isadditionally used as a brake holder for a second floating-caliper-typecomponent of the disc brake device. In this arrangement, thefloating-caliper-type component straddles the second brake disc andbrake pads being arranged on either side of this brake disc and isdisplaceably mounted on the first fixed-caliper-type component. Thefloating-caliper-type component comprises another hydraulic actuatingdevice in order to move the corresponding brake pads into abutment onthe second brake disc when the brake is applied. The disc brake deviceconsequently has a fixed-caliper and a floating-caliper componentemboxed in each other. This type of construction is unnecessarilycomplicated and, what is more, requires three actuating devices in orderto press the individual brake pads accordingly against the associatedbrake discs.

BRIEF SUMMARY OF THE INVENTION

In view of the above, the invention is based on a disc brake having atleast two friction rings which, at an axial distance from each other,are stationarily arranged on a rotatable hub, having brake padsassociated with each friction ring and being displaceably arranged ineach case on both sides of the friction ring. Based on these conditions,an object of the invention is to disclose a disc brake with at least twofriction rings which, compared to prior art types of construction,exhibits a simple overall construction that can be realized at lowcosts. The axially stationary friction rings allow economizing asophisticated axial guiding of the friction rings, as it has beenfrequently customary in previous types of construction. Further, theemployment of one single brake caliper with a displaceable secondactuating device reduces the effort in construction for the disc brake.The actuating devices, i.e. the first and/or the second actuatingdevice, can principally generate the brake application force within thedisc brake, for example, hydraulically, electrically,electromagnetically, electromotively, or in any other suitable fashion.

This object is achieved for the generic disc brake mentioned hereinaboveby a brake caliper straddling all friction rings and the associatedbrake pads and including a first actuating device in at least one brakecaliper portion that extends axially beside the friction rings and asecond actuating device that is arranged between two friction rings, isactive axially at least on one side and acts on at least one brake padarranged between two friction rings.

The use of two or more friction rings with associated brake padsprincipally allows realizing very high rates of braking power. Thus, thebrake caliper includes a first actuating device in a brake caliperportion that extends axially beside the friction rings in order todisplace at least one brake pad directly against the associated frictionring in a braking operation. When the second actuating device operatesonly on one side, this actuating device is still able to expedientlyoperate both with a fixed-type caliper and a floating caliper, providedit is floatingly mounted. When it is stationarily arranged on thecaliper of a fixed-caliper brake, for example, two serially arranged,one-sidedly operating actuating devices are required which operate inparallel and press the corresponding brake pads against the frictionrings.

A significantly simpler design is achieved for the disc brake of theinvention when the second actuating device is acting on both sides andacts on two brake pads arranged between two friction rings. Although thetype of driving the actuating device is not important for the inventionat topic, especially a hydraulic drive is very well suited as a drivingmechanism because it is herein safeguarded that the same amount ofpressure is applied to the two brake pads.

The invention is well applicable to a fixed-caliper brake wherein thefriction rings do not change their position in relation to the caliper.The actuating device can then act in a two-sided manner because twoserially disposed pistons are provided e.g. in a cylinder and areactuated by the same pressure source. It is not necessary in this caseto arrange the actuating device so as to be floating in an axialdirection, whereby a simpler design for the brake is achieved. When theactuating device is floatingly arranged, it is also possible for it toact in only one direction, because in this case e.g. the housing of thedevice can press against the one brake pad, while the piston can pressagainst the other brake pad.

In improving the invention, its employment in a floating-caliper brakeis especially advisable, wherein the second actuating device can befixed or displaceably arranged at the caliper or a brake holder of thefloating caliper that is fixed in relation to the vehicle, or at anyother component that is fixed in relation to the vehicle, respectively.Only one single first actuating device in the floating caliper isnecessary in such a case. The use of a brake holder, with acorresponding design, provides the additional advantage of guiding thebrake pads on the brake holder in an axially displaceable fashion and ofsupporting them in a circumferential direction.

A favorable first embodiment of the second actuating device between twofriction rings is achieved in that the second actuating device is guidedso as to be displaceable directly on the brake caliper. The brakecaliper can then be configured as a floating caliper and as a fixedcaliper. The second actuating device is preferably acting on both sidesand, thus, additionally allows pressing the brake pads interposedbetween two friction rings against the associated friction rings.

In an alternative variant of the disc brake, the second actuating deviceis displaceably mounted on a component fixed to the vehicle, inparticular on a brake holder fixed to the vehicle. In this arrangement,the brake caliper is designed as a floating caliper being displaceablymounted in relation to a component fixed to the vehicle, above all tothe brake holder fixed to the vehicle. This type of construction isadditionally improved by means of a brake holder fixed to the vehicle, aportion of which projects axially over at least one friction ring,wherein at least one brake pad and the second actuating device aredisplaceably guided on this brake holder portion. It is then possible todisplaceably mount both the brake pads and the second actuating deviceon the same guiding portion of the brake holder. This reduces themachining effort for the brake holder.

Because the initial position of the floating caliper relative to thebrake holder will change in the course of time due to the wear of the(outboard) friction lining, it is favorable to fix the second actuatingdevice at the caliper. This condition will additionally facilitate thesupply of hydraulic pressure when a hydraulic drive is used. However,the actuating device can also be mounted on the brake holder, therebyenabling it to automatically follow the change in position of thecaliper in relation to the brake holder.

A particularly simple structure for a two-sidedly acting secondactuating device is obtained because the actuating device includes twopistons that limit a working chamber hydraulically, and because theworking chamber is connected to the hydraulic circuit feeding the firstactuating device. It is hereby ensured in a simple fashion that in eachcase the brake pads can be applied with equal pressure to either side ofthe two friction rings. In this arrangement, the pistons can be guidedin a cylinder lying axially behind one another (FIG. 5) or also beingdisplaceably nested, with the outside piston being displaceably guidedin a housing (FIG. 3).

When the two pistons are arranged one behind the other in a cylinder(FIG. 5) and the cylinder is rigidly connected to the caliper of afloating-caliper brake, attention must be paid to the fact that theposition of the cylinder changes with the position of the caliper as theoutside brake pad wears off. Therefore, the second piston pointing tothe outside friction ring shall be longer than the opposite first pistonaccording to the invention because the cylinder along with the calipermoves inwards, while simultaneously the back plate of the brake padacted upon by the second piston moves (relatively) outwards. When theserules are observed, it is possible to keep the overall length of thesecond actuating device very short.

When it is desired to arrange the actuating device so as to bedisplaceable on the holder arms of the brake holder, it is advisableaccording to an improvement of the invention to connect the secondactuating device to one of the two brake pads being arranged between thetwo friction rings. This way a unit can be achieved which is composed ofa brake pad and the second actuating device, what will reduce the numberof the necessary individual components and the weight of the disc brake.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a partial cross-sectional spatial view of a firstembodiment of a disc brake having two stationary friction rings, withassociated brake pads and a floating caliper.

FIG. 2 shows a partial cross-sectional spatial view of an associatedbrake holder having brake pads for a floating-caliper disc brakeaccording to FIG. 1.

FIG. 3 shows a cross-sectional view of a disc brake according to FIGS. 1to 2.

FIG. 4 shows an enlarged spatial view of a second actuating device ofFIGS. 1 to 3.

FIG. 5 shows a view of a cross-section taken through a disc brake of theinvention as a second embodiment in a first variant.

FIG. 6 shows a view of a cross-section taken along line A-A of the discbrake of FIG. 5.

FIG. 7 shows a cross-sectional view of an alternative design of thesecond embodiment.

FIG. 8 shows a spatial view of the second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The disc brake 1 for a motor vehicle of the invention as shown in FIGS.1 to 4 comprises two friction rings 2, 3 that are fixed to a rotatablewheel hub 4. In this arrangement, the friction rings 2, 3, at aninvariable axial distance, are unrotatably secured to the wheel hub 4 orintegrally shaped thereat. In particular, the friction rings 2, 3 can bedetachably fastened to the wheel hub 4. The friction rings 2, 3cooperate with associated bake pads 6 to 9 of the disc brake 1 by way ofcorresponding friction surfaces 5 being respectively provided on bothsides in order to thereby achieve braking power in the case of a brakingoperation. Further, the disc brake 1 comprises a brake holder 10 fixedto the vehicle and projecting with two holder arms 11 over the twofriction rings 2, 3 in an axial direction. Herein the brake holder 10 iseither fixed to the vehicle or integrated into a component fixed to thevehicle, e.g. a steering knuckle. The brake pads 6 to 9 are axiallydisplaceably guided and tangentially supported on the holder arms 11.The indications of direction refer to the axis of rotation of thefriction rings in this context. In detail, the brake pads 6 to 9 eachinclude tangentially lateral guiding extensions 12 being received incorrespondingly shaped guiding recesses 24 of the holder arms 11 in asubstantially form-locking fashion. Thus, peripheral brake forces at thebrake pads 6 to 9 that develop during operation of the disc brake 1 canbe discharged to the holder arms 11 or the brake holder fixed to thevehicle, respectively. To additionally reinforce the holder arms 11, itis favorable to interconnect said arms by a web 25 (see FIG. 3) thatextends in a substantially tangential direction. This arrangementreduces the degree of the elastic deformation of the holder arms 11 onaccount of peripheral brake forces.

Besides, a floating caliper 13 is displaceably mounted on the brakeholder 10 and straddles the friction rings 2, 3 and the brake pads 6 to9 arranged in each case on both sides of the friction rings 2, 3. Forthe displaceable arrangement of the floating caliper 13, guiding devices(not shown), e.g. pin guides, are provided that act in particularbetween the brake holder 10 and the floating caliper 13. The floatingcaliper 13 principally comprises two caliper legs 14, 15 that extendlaterally beside the friction rings 2, 3 and extend generally inparallel to the friction rings 2, 3. The two caliper legs 14, 15 areinterconnected by a bridge portion 16 that projects axially over thefiction rings 2, 3. The floating caliper 13 has preferably an integraldesign. It is however principally possible for it to consist of severalmembers that have to be interconnected.

The floating caliper 13 has an integral and frame-type design in theembodiments according to FIGS. 1 to 4. However, other types ofconstruction of a brake caliper are also feasible for a disc brake 1 ofthe invention.

To apply the disc brake 1 during a braking operation, the floatingcaliper 13 includes a first actuating device 17 in the caliper leg thatis axially inwards with respect to the vehicle, said actuating deviceacting on at least one brake lining 6 to 9. The first actuating device17 is designed as a hydraulic actuating device 17 in the presentembodiment, including a cylinder 18 integrated in the caliper leg 14 anda piston 19 displaceably arranged therein. Piston 19 enables the firstactuating device 17 to apply the axially inward brake pad 6 directlyagainst the associated friction ring 2 during a braking operation, whilethe axially outward brake pad 9 is pressed indirectly against theoutward friction ring 3 due to an axial displacement of the floatingcaliper 13.

In addition, a second actuating device 20 is arranged between thefriction rings 2, 3 and acts on the brake pads 7, 8 disposed between thefriction rings 2, 3. Likewise the second actuating device 20 ishydraulically operable and comprises a cylinder 21 and a piston 22displaceably mounted therein. Principally, the two actuating devices 17,20 need not be supplied hydraulically with a brake-applying force.Similarly, other actuation devices 17, 20 may also be used, which arefed with actuating energy or brake-applying force in an electrical,electromotive, electromagnetical, piezoelectrical, or any othercomparable manner. The second actuating device 20 is then acting axiallyon both sides so that during braking operation both brake pads 7, 8arranged between the friction rings 2, 3 can be pressed almostsimultaneously against the associated friction surface 5. In the secondactuating device 20 according to FIGS. 1 to 4, a braking operationcauses the piston 22 to be urged against a brake pad 8, while thecylinder 21 is urged against the other brake pad 7 due to a reactionforce. Alternatively, a second actuating device 20 with a cylinder 21open on either side can be used, and two pistons 22 associated with thebrake pads 7, 8 are displaceably received in cylinder 21.

The second actuating device 20 is guided in an axially displaceablemanner within the disc brake 1 due to the axially stationary arrangementof the friction rings 2, 3. In particular, the second actuating device20 is connected to a carrier 23 which in turn is displaceably guided onthe brake holder 10. In principle, the second actuating device 20 canalso be guided displaceably on any other component fixed to the vehicle.The carrier 23 is displaceably guided on the brake holder 10 in theembodiment of the disc brake 1 shown in FIGS. 1 to 4. To this end, thecarrier 23 and the brake pads 6 to 9 include lateral guiding extensions12 which in turn are received in a substantially form-locking manner inthe guiding recesses 24 of the holder arms 11. Thus, the guidingrecesses 24 in the holder arms 11 can be used for the displaceableguiding of both the brake pads 6 to 9 and the second actuating device20. This simplifies the manufacture of the brake holder 10 in total. Theconfiguration of especially the second actuating device 20 according tothe invention will thus allow uniformly pressing all brake pads 6 to 9against the respective friction surfaces 5 of the friction rings 2, 3. Abrake caliper that is possibly configured in one part can be used inthis case.

The design variant shown in the Figures can be simplified in that thesecond actuating device 20 is directly coupled to one of the brake pads7, 8 arranged between the friction rings 2, 3. The second actuatingdevice 20 along with the respective brake pad 7, 8 is displaced axiallyin the holder arms 11. To this end, the second actuating device 20 isconnected to the respective brake pad 7, 8 preferably by way of thecylinder 21.

The solution according to the invention is of course not limited to theembodiment shown in the Figures. It is principally also possible toapply a disc brake design according to the invention in arrangementswith more than two friction rings positioned in an axially stationarymanner.

Further, it is possible to arrange the second actuating device 20 in adisplaceable manner on the floating caliper 1. A construction of thistype is advisable in the absence of a brake holder 10 with holder arms11 straddling the friction rings 2, 3.

In addition, the second actuating device can be arranged in an axiallystationary fashion on a component fixed to the vehicle, in particular onthe brake holder, according to an alternative not shown. To this end itis necessary to configure the stationary second actuating device 20 soas to be acting axially on both sides. This necessitates the provisionof actuating elements on both axial sides of the second actuating device20, said actuating elements being each displaceably mounted in thesecond actuating device 20 and acting on one of the brake pads 7, 8.

Eventually, it is also feasible to configure the brake caliper of a discbrake of the invention as a fixed caliper mounted on the vehicle. Inthis arrangement, the second actuating device 20 acting on both sidesbetween two axially stationary friction rings 2, 3 would have to beaxially displaceably guided either on a component fixed to the vehicle,e.g. a brake holder, or directly on the fixed caliper. Alternatively,the second actuating device 20 acting on both sides can be arranged inan axially stationary fashion on a component fixed to the vehicle.Compared to designs having a floating caliper, however, two firstactuating devices 17 are required when a fixed caliper is used in orderto be able to apply a brake-applying force to the axially outward/inwardbrake pads 6, 9.

The second embodiment of a disc brake of the invention is illustrated inFIGS. 5 to 8. Herein the friction rings 2, 3 are either shapedintegrally at the hub or detachably secured thereat. Associated with thefriction rings 2, 3 are brake pads 6, 7, 8, 9, which, for achievingbraking power during a braking operation, cooperate tribologically withthe friction rings. The disc brake further comprises a floating caliper1 straddling the friction rings 2, 3 and the associated brake pads 6, 7,8, 9 (see FIG. 5).

The floating caliper 13 of the disc brake shown comprises a firstactuating device 17 arranged in a caliper leg in order to be able duringbraking operation to urge an axially inward brake pad 6 directly and anaxially outward brake pad 9 indirectly due to caliper displacementagainst the associated friction ring 2, 3.

Disposed between the axially immovable friction rings 2, 3 is anothersecond actuating device 20 that is active on both sides and, thus, whenactivated in the case of a braking operation presses the brake pads 7, 9arranged between the friction rings 2, 3 against the associated frictionrings. As this occurs, the second actuating device 20 is rigidlyconnected to the floating caliper 1 with the result of achieving astructural unit (see FIG. 8). The two actuating devices can be fed withactuating energy or force e.g. hydraulically, electrically,electromechanically, electromagnetically, electromotively,piezoelectrically, or in any other appropriate fashion. The rigidconnection 26 between the floating caliper 1 and the second actuatingdevice 20 will thus enable an uncomplicated energy supply of the secondactuating device 20 by suitably configuring the supply lines, above allwithin the floating caliper 1. In the variants in FIGS. 5 to 8 the twoactuating devices are designed hydraulically, in each case with acylinder and a piston displaceably mounted therein. The second actuatingdevice 20 has two pistons 37, 38 accommodated in the joint cylinder 21(FIGS. 5 to 6). These pistons 37, 38 are axially active in oppositedirections and press the brake 7, 8 from inwards against the associatedfriction rings 2, 3 during braking operation, i.e. pressurization of thesecond actuating device. In the illustrated variant, the primary piston37 brings about the displacement of the floating caliper 1 and acompensation of brake pad wear, while the secondary piston 38 is usedfor the inevitable tolerance compensation. Therefore, the secondarypiston 38 may have an axially shorter design.

To ventilate and bleed the hydraulic pressure chamber of the secondactuating device, channels 27, 28, 29, 30 are provided, depending on theinstallation position, which are partly closed from the outside by meansof balls 31, 40 in order to seal openings existing for reasons ofmanufacture.

Another embodiment of the disc brake 1 according to FIG. 7 shows apossibility of reducing the axial mounting space of the second actuatingdevice 20. The hydraulically actuated second actuating device 20comprises a first primary piston 32 that acts on the brake pad 8 in anaxially outward direction and two secondary pistons 33 which oppositelyact on the other brake pad 7 in an axially inward direction. In thisarrangement, the primary piston 32 and the secondary pistons 33 arearranged in parallel inside the second actuating device. Preferably adesign according to FIG. 7 is chosen, according to which two smallersecondary pistons 33 having an equal resulting piston surface like theprimary piston 32 are used. Of course it is also possible to reversesuch a dimensioning so that a large secondary piston 33 and two smallerprimary pistons 32 can be employed in a similar fashion. The hydraulicpressure chambers of the second actuating device are ventilated and bledpreferably similar to the embodiment according to FIGS. 5, 6, 8.

In the course of the simplification of manufacture, the floating caliper1 is preferably configured in two parts, and the two parts areinterconnected. The configuration of the disc brake in particular withthe second actuating device between the friction rings 2, 3, as shown inthe invention, is of course not limited to the embodiments shown in theFigures. The brake caliper of the disc brake into which also the secondactuating device is integrated can alternatively be designed as a fixedcaliper. The precondition for this is a second actuating device 20acting axially on both sides. In addition, the configuration of a discbrake according to the invention is also applicable to arrangementshaving more than two friction rings, which are connected to a rotatablehub at a fixed axial distance.

The advantage of a disc brake of the invention having a brake caliperinto which the second actuating device is integrated is the simpleoverall construction that permits low-cost manufacture. Besides, anaxially very compact disc brake is achieved, favorably necessitating asmall mounting space. In addition, the configuration of the brakecaliper allows dividing the floating caliper, which is advantageous interms of manufacturing engineering. The entire disc brake is basicallyinsensitive to corrosion signs due to the axially stationary arrangementof the friction rings and the integration of the second actuating deviceinto the brake caliper. As regards a comfortable brake pad guide orfloating caliper guide (in a floating caliper design), reference can bemade to solutions in the prior art that are functionally reliable to asufficient degree.

1.-9. (canceled)
 10. A disc brake having at least two friction ringswhich, at an axial distance from each other, are stationarily arrangedon a rotatable hub, with brake pads associated with each friction ringand being displaceably arranged on both sides of the friction ring,comprising a brake caliper straddling all friction rings and theassociated brake pads and including a first actuating device in at leastone brake caliper portion that extends axially beside the frictionrings, and a second actuating device that is arranged between twofriction rings, is acting axially at least on one side and acts on atleast one brake pad arranged between two friction rings.
 11. The discbrake as claimed in claim 10, wherein the second actuating device isacting on both sides and acts on two brake pads arranged between twofriction rings.
 12. The disc brake as claimed in claim 11, wherein thebrake is a fixed-caliper brake which includes a first actuating deviceon both sides, in each case in brake caliper portions of the fixedcaliper that extend axially beside the friction rings, and in that thesecond actuating device is fixed to the caliper or displaceably arrangedthereat.
 13. The disc brake as claimed in claim 11, wherein the brake isa floating-caliper brake and the second actuating device is fixed at thecaliper.
 14. The disc brake as claimed in claim 11, wherein the brake isa floating-caliper brake and the second actuating device is fixed at abrake holder of the floating caliper that is fixed in relation to thevehicle.
 15. The disc brake as claimed in claim 11, wherein the brake isa floating-caliper brake and the second actuating device is displaceablyarranged at the caliper.
 16. The disc brake as claimed in claim 11,wherein the brake is a floating-caliper brake and the second actuatingdevice is displaceably arranged at a brake holder of the floatingcaliper that is fixed in relation to the vehicle.
 17. The disc brake asclaimed in claim 11, wherein the second actuating device includes twopistons limiting a working chamber hydraulically, and in that theworking chamber is connected to the hydraulic circuit feeding the firstactuating device.
 18. The disc brake as claimed in claims 13, whereinthe two pistons being in alignment with each other are displaceablyarranged in a cylinder open on both sides, in that the cylinder issecured to the caliper, and in that the hydraulic connection to thehydraulic circuit extends from the caliper through the connection intothe cylinder.
 19. The disc brake as claimed in claim 18, wherein thebrake is a floating-caliper brake, in that the first piston facing thefirst actuating device is shorter than the second piston.
 20. The discbrake as claimed in claim 18, wherein the caliper, the connectionbetween caliper and cylinder, and the cylinder are formed of an integralcast piece.
 21. The disc brake as claimed in claims 17, wherein the twopistons being in alignment with each other are displaceably arranged ina cylinder open on both sides, in that the cylinder is secured to thecaliper, and in that the hydraulic connection to the hydraulic circuitextends from the caliper through the connection into the cylinder. 22.The disc brake as claimed in claim 21, wherein the brake is afloating-caliper brake, in that the first piston facing the firstactuating device is shorter than the second piston.
 23. The disc brakeas claimed in claim 21, wherein the caliper, the connection betweencaliper and cylinder, and the cylinder are formed of an integral castpiece.
 24. The disc brake as claimed in claim 10, wherein the secondactuating device is connected to a brake pad that is displaceably guidedon the brake holder portion.